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How Much Testing is Enough?


Governments around the world are criticized for their apparent slow introduction of testing and achieving inadequate volume to control the COVID-19 outbreak.  The World Health Organization maintains that if less than ten percent of those randomly tested yield SARS-CoV-2 the virus responsible for COVID-19 on sampling, then a country is adequately served. In contrast, epidemiologists experienced in influenza outbreaks maintain that a three percent positive level indicates adequacy of testing.  Currently assays to demonstrate the presence of SARS-CoV-2 in the U.S., yield positives in the region of 20 percent for selected individuals, either in contact with patients or demonstrating clinical signs. These results are therefore from a biased symptomatic sample and do not reflect the prevalence of the infection in the population.


Testing for antibody


According to a column authored by Teresa Hanafin in The Boston Globe on Thursday, April 30th, Dr. Antony Fauci considers that three million tests are required each week for the U.S., approximately twice the 1.6 million conducted at present.  Researchers at Harvard University recommend five million tests per week distributed at random among various states, depending on the prevalence rate.  The Harvard Global Health estimate was based on the WHO 10 percent level and indicated that many states are deficient with respect to numbers of tests performed.


The Boston Globe, Fast Forward column pointed to the fact that some states, including Florida and Georgia, are relaxing social distancing and home confinement restrictions with a totally inadequate capacity to conduct tests.  It is estimated that Georgia, home state of the CDC requires 10,000 tests daily but has been averaging only 4,000.


The CVS Health Corporation announced on April 27th that it would commence a comprehensive testing program at approximately 1,000 sites to conduct 1.5 million tests each month depending on availability of supplies.  Between CVS, Rite Aid, Walgreens, and Walmart, seventy testing sites have been established in parking lots for drive-through sampling.  This initiative is supported by the CDC that will soon release new guidelines to identify asymptomatic individuals in high-risk occupations.  It is now recognized that infection with COVID-19 virus can occur with people transmitting the pathogen without necessarily being aware of their condition.


As we ease social restrictions adequate testing is required to identify those infected in order to quarantine them and to investigate and evaluate their contacts. This approach applied in South Korea was effective in “flattening the curve” and reducing the incidence rate compared to other nations in Asia and the EU. Fortunately the Roche rapid test has now received provisional FDA approval and will add to testing capacity.


The quicker that COVID-19 can be suppressed the safer will be policies designed to restore the economy. Resumption of activities in the food service sector is of specific and immediate concern for the egg-production industry. As restaurants re-open, shell eggs will move back from the retail to the food service sector reversing the trend of the past six weeks. It will only be with re-opening of schools and universities and with more travel that the food service sector will be resuccitated removing the output of 10 to 20 million shell eggs from the retail market with obvious implications for price.


Establishing the prevalence of antibody in the populations of specific areas and the incidence rate through antigen detection will be critical to guiding policy until an effective vaccine becomes available. Relaxing COVID-19 restrictions without adequate epidemiologic data will result in resurgence in infection and more misery for our industry. The basic question of “how much testing do we need” is not an absolute number but is determined by incidence rates and will change over time and circumstances. Our epidemiologists can prepare recommendations based on science to guide politicians to devise and implement policies that will be effecively a compromise between public health and our economy. Intrusion of armed protesters into legislative buildings to intimidate lawmakers and governors are not a realistic counterpoint to science and established facts relating to the progress of the pandemic.